The present invention relates to building blocks and, more particularly, to interfitting construction units and walls constructed of the units without mortar.
Many free-standing and retaining walls are constructed either from poured concrete or from bricks or concrete blocks held together by mortar. In the case of poured concrete, skilled labor is required to construct forms, and pour and finish the concrete to form the wall. Footings must also be provided and, as a result, the intensity of labor necessary to construct a poured concrete wall involves high labor costs. Similarly, in constructing a wall of bricks or concrete blocks, skilled masons are required to apply the mortar and lay the blocks, again involving high labor costs.
Systems are known which employ modular construction units which fit together without mortar to form a wall. Thus, some of the cost involved in the labor-intensive conventional poured concrete, brick or concrete block walls is avoided. However, most of the known mortarless units have shapes which require them to be produced in special machinery or at a low output rate, or both, which results in the cost of the units to be high. In addition, the absence of mortar makes it easier for water to flow into crevices between units and remain there, especially in retaining wall applications. If this occurs in a region where there is freezing, the water freezes and expands, breaking up the units. Even where there is no freezing, the trapped water causes efflorescence; that is, the water seeps into the units, dissolves salts naturally present in the clay or cementitious material of which the units are made, and carries the salts to the surfaces of the units, where the salts cause unsightly stains.
Some of the known mortarless units can be stacked only at an angle, thereby rendering them unsuitable in constructing free-standing walls, and useful only in constructing retaining walls. Some of the units which stack at an angle require backfilling to be performed after each course is laid in a retaining wall. Some of the known mortarless units which can be stacked essentially vertically have only one finished face, that is, only one face having an acceptable appearance. At least one known mortarless system employs separate fiberglass pins which are inserted into holes in the top surfaces of units on the job site in order to provide interfitting between adjacent courses.
Some of the units require separate footings or special wedge-shaped pieces to orient the wall at a desired angle, while other retaining wall systems require the earth under the wall to be shaped to a predetermined angle. Many of the known mortarless units are not adapted to cooperation with piers whereby walls of greater height can be constructed. Due to their mortarless nature, the units of some systems can be easily disassembled by vandals. In some systems, the units are too heavy to be moved and assembled without mechanical equipment.